New JSON API for contacts?
Some hidden code in Google Video points to a new contact picker -- something I have always thought would make sense in Gmail when you are deciding where to send an email (when you want to choose from a list). That is currently a little tough to do when the only thing in your arsenal is auto-completion when you start typing.
While taking a peek at the source code, I found a reference to the JSON API they are using to retrieve personal contact information associated with the currently logged in user. Click here to see the list of contacts in your Gmail for example.
The script you see there isn't exactly usable in web applications in its current format, but it would be very easy for any windows application to pull up that page and get your list of contacts (assuming you are logged in).